.. highlightlang:: sh
.. ATTENTION: You probably should update Misc/python.man, too, if you modify
this file.
.. _using-on-general:
Command line and environment
============================
The CPython interpreter scans the command line and the environment for various
settings.
.. impl-detail::
Other implementations' command line schemes may differ. See
:ref:`implementations` for further resources.
.. _using-on-cmdline:
Command line
------------
When invoking Python, you may specify any of these options::
python [-BdEiOQsRStuUvVWxX3?] [-c command | -m module-name | script | - ] [args]
The most common use case is, of course, a simple invocation of a script::
python myscript.py
.. _using-on-interface-options:
Interface options
~~~~~~~~~~~~~~~~~
The interpreter interface resembles that of the UNIX shell, but provides some
additional methods of invocation:
* When called with standard input connected to a tty device, it prompts for
commands and executes them until an EOF (an end-of-file character, you can
produce that with *Ctrl-D* on UNIX or *Ctrl-Z, Enter* on Windows) is read.
* When called with a file name argument or with a file as standard input, it
reads and executes a script from that file.
* When called with a directory name argument, it reads and executes an
appropriately named script from that directory.
* When called with ``-c command``, it executes the Python statement(s) given as
*command*. Here *command* may contain multiple statements separated by
newlines. Leading whitespace is significant in Python statements!
* When called with ``-m module-name``, the given module is located on the
Python module path and executed as a script.
In non-interactive mode, the entire input is parsed before it is executed.
An interface option terminates the list of options consumed by the interpreter,
all consecutive arguments will end up in :data:`sys.argv` -- note that the first
element, subscript zero (``sys.argv[0]``), is a string reflecting the program's
source.
.. cmdoption:: -c
Execute the Python code in *command*. *command* can be one or more
statements separated by newlines, with significant leading whitespace as in
normal module code.
If this option is given, the first element of :data:`sys.argv` will be
``"-c"`` and the current directory will be added to the start of
:data:`sys.path` (allowing modules in that directory to be imported as top
level modules).
.. cmdoption:: -m
Search :data:`sys.path` for the named module and execute its contents as
the :mod:`__main__` module.
Since the argument is a *module* name, you must not give a file extension
(``.py``). The ``module-name`` should be a valid Python module name, but
the implementation may not always enforce this (e.g. it may allow you to
use a name that includes a hyphen).
Package names are also permitted. When a package name is supplied instead
of a normal module, the interpreter will execute ``.__main__`` as
the main module. This behaviour is deliberately similar to the handling
of directories and zipfiles that are passed to the interpreter as the
script argument.
.. note::
This option cannot be used with built-in modules and extension modules
written in C, since they do not have Python module files. However, it
can still be used for precompiled modules, even if the original source
file is not available.
If this option is given, the first element of :data:`sys.argv` will be the
full path to the module file. As with the :option:`-c` option, the current
directory will be added to the start of :data:`sys.path`.
Many standard library modules contain code that is invoked on their execution
as a script. An example is the :mod:`timeit` module::
python -mtimeit -s 'setup here' 'benchmarked code here'
python -mtimeit -h # for details
.. seealso::
:func:`runpy.run_module`
Equivalent functionality directly available to Python code
:pep:`338` -- Executing modules as scripts
.. versionadded:: 2.4
.. versionchanged:: 2.5
The named module can now be located inside a package.
.. versionchanged:: 2.7
Supply the package name to run a ``__main__`` submodule.
sys.argv[0] is now set to ``"-m"`` while searching for the module
(it was previously incorrectly set to ``"-c"``)
.. describe:: -
Read commands from standard input (:data:`sys.stdin`). If standard input is
a terminal, :option:`-i` is implied.
If this option is given, the first element of :data:`sys.argv` will be
``"-"`` and the current directory will be added to the start of
:data:`sys.path`.
.. seealso::
:func:`runpy.run_path`
Equivalent functionality directly available to Python code
.. describe::